Que Su as a replacement for Cuyo

Hola Devin P.

While "que su" isn't technically a direct replacement for "cuyo", I can see why there might be some confusion, especially since both can relate possession to a noun.

Cuyo is a relative possessive adjective that agrees with the noun it modifies (the thing possessed), not with the possessor.

For example:

Que su is actually a combination of two separate words that isn't grammatically standard in formal Spanish for expressing "whose". However, in informal spoken Spanish, you might hear constructions like:

That said, this construction is generally considered incorrect in formal Spanish. The proper alternatives to "cuyo" (which is quite formal and rarely used in everyday speech) would be:

1. Restructuring the sentence: El hombre que tiene el coche rojo.
2. Using "de quien/de quienes": El hombre de quien el coche es rojo. (Though this is also quite formal)

In practice, native speakers often avoid "cuyo" altogether in conversation by rephrasing their sentences, which might be why you encountered "que su" somewhere, it's a common informal workaround, even though it's not grammatically correct.

I hope this helps clarify things for you.

Saludos

Silvia